Squats make the outer part of the thigh muscle near the knee bigger than leg extensions do.
Scientific Claim
Back squat training leads to greater hypertrophy of the vastus lateralis muscle at the distal site in untrained young women after 8 weeks, with a 18.2% increase compared to 11.2% with leg extensions.
Original Statement
“Conversely, the SQ showed greater increases in VL at the distal site (+18.2% vs. +11.2%; p < 0.001).”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
RCT design permits causal inference, but lack of blinding reduces confidence. 'Leads to' is appropriately softened to probabilistic language given potential performance bias.
More Accurate Statement
“Back squat training likely leads to greater hypertrophy of the vastus lateralis muscle at the distal site in untrained young women after 8 weeks, with a 18.2% increase compared to 11.2% with leg extensions.”
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.
Systematic Review & Meta-AnalysisLevel 1aWhether back squats consistently produce greater distal vastus lateralis hypertrophy than leg extensions across populations.
Whether back squats consistently produce greater distal vastus lateralis hypertrophy than leg extensions across populations.
What This Would Prove
Whether back squats consistently produce greater distal vastus lateralis hypertrophy than leg extensions across populations.
Ideal Study Design
A meta-analysis of 12+ RCTs comparing squats and leg extensions in untrained adults, using standardized ultrasound protocols to measure distal vastus lateralis thickness after 8–12 weeks of matched volume training.
Limitation: Cannot determine if differences are due to mechanical tension, metabolic stress, or neural adaptation.
Randomized Controlled TrialLevel 1bIn EvidenceCausal effect of back squats on distal vastus lateralis hypertrophy vs. leg extensions.
Causal effect of back squats on distal vastus lateralis hypertrophy vs. leg extensions.
What This Would Prove
Causal effect of back squats on distal vastus lateralis hypertrophy vs. leg extensions.
Ideal Study Design
A double-blind RCT of 120 untrained women aged 18–30, randomized to 8 weeks of back squats or leg extensions (3×8–12 RM, 2×/week), with blinded ultrasound assessors measuring distal vastus lateralis thickness at baseline and post-intervention.
Limitation: Does not assess long-term maintenance or transfer to functional performance.
Prospective Cohort StudyLevel 2bReal-world association between squat frequency and distal vastus lateralis growth.
Real-world association between squat frequency and distal vastus lateralis growth.
What This Would Prove
Real-world association between squat frequency and distal vastus lateralis growth.
Ideal Study Design
A 1-year cohort tracking 300 gym-goers who self-select squats or leg extensions, with quarterly ultrasound measurements of distal vastus lateralis thickness, adjusting for total leg volume and protein intake.
Limitation: Cannot control for self-selection bias or training intensity differences.
Evidence from Studies
Supporting (1)
Comparison of Muscle Hypertrophy and Strength Adaptations Induced by Back Squat and Leg Extension Resistance Exercises.
The study found that doing back squats made the lower part of the big thigh muscle grow more than doing leg extensions, just like the claim said.